أسئلة الـ development of respiratory system (ريتين ثانية أناتومي)
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Questions and Answers

What is the primary development that occurs during the pseudo-glandular stage of lung development?

Only terminal bronchioles are formed during the pseudo-glandular stage.

During the canalicular stage of lung development, what key structures are formed?

The terminal bronchioles divide into respiratory bronchioles and alveolar ducts.

Identify the types of cells present in primitive alveoli during the saccular stage.

Type I and Type II pneumocytes are present in primitive alveoli.

What condition results from failed recanalization of the larynx?

<p>Laryngeal atresia results from failed recanalization of the larynx.</p> Signup and view all the answers

What is a tracheo-esophageal fistula and what causes it?

<p>A tracheo-esophageal fistula is caused by abnormal partitioning of the cranial part of the foregut due to issues with the tracheo-esophageal septum.</p> Signup and view all the answers

What embryonic origin do the facial muscles derive from, and which nerve supplies them?

<p>The facial muscles derive from the mesoderm of the 2nd pharyngeal arch and are supplied by the facial nerve.</p> Signup and view all the answers

Which structures are involved in the formation of the upper and lower lips?

<p>The upper lip is formed by the maxillary process except for the philtrum from the inter-maxillary segment, while the lower lip is formed by the mandibular processes.</p> Signup and view all the answers

How do the nasal cavities develop and what membrane separates them from the oral cavity initially?

<p>The nasal cavities develop from deepening nasal pits that form primitive nasal sacs, separated from the oral cavity by the oro-nasal membrane.</p> Signup and view all the answers

What is the embryonic source of the nasal septum?

<p>The nasal septum develops from the inter-maxillary segment.</p> Signup and view all the answers

What are the consequences of the failure to fuse the maxillary and lateral nasal folds?

<p>The failure results in an oblique facial cleft, leading to exposure of the nasolacrimal duct on the surface.</p> Signup and view all the answers

Differentiate between a median cleft lip and a unilateral cleft lip.

<p>A median cleft lip results from the failure of fusion between medial nasal folds or mandibular processes, while a unilateral cleft lip occurs between the medial nasal fold and maxillary process.</p> Signup and view all the answers

What is the defining feature of macrostomia and its embryological cause?

<p>Macrostomia is characterized by a large mouth opening due to the failure of fusion between the maxillary and mandibular processes.</p> Signup and view all the answers

What constitutes the primary palate and what does it carry?

<p>The primary palate is an anterior triangular area that carries the four incisors.</p> Signup and view all the answers

What are the pharyngeal arches, and how are they arranged?

<p>The pharyngeal arches are 6 mesodermal thickenings on each side of the pharynx, arranged cranio-caudally.</p> Signup and view all the answers

What forms the floor of the stomodaeum and when does it rupture?

<p>The floor of the stomodaeum is formed by the buccopharyngeal membrane, which ruptures in the 5th week.</p> Signup and view all the answers

Identify the key processes involved in the development of the face and nose.

<p>The key processes include the fronto-nasal process, two maxillary processes, and two mandibular processes.</p> Signup and view all the answers

What role do nasal placodes play in the development of the nose?

<p>Nasal placodes are ectodermal thickenings that invaginate to form nasal pits, leading to the development of the nose.</p> Signup and view all the answers

What structures are produced by the fusion of the medial nasal folds?

<p>The fusion of the medial nasal folds produces the nasal septum, philtrum of the upper lip, central part of the upper jaw, primary palate, and tip of the nose.</p> Signup and view all the answers

How do the maxillary processes influence the formation of the upper lip?

<p>The maxillary processes grow medially to fuse with the medial nasal folds, forming the upper lip.</p> Signup and view all the answers

What anatomical structures fuse to form the secondary palate?

<p>The secondary palate is formed by two shelf-like projections arising from the inner side of maxillary processes that fuse in the midline with the descending nasal septum.</p> Signup and view all the answers

What is the main cause of anterior clefts of the palate?

<p>Anterior clefts of the palate are caused by the failure of the palatine shelves to fuse with the premaxilla.</p> Signup and view all the answers

In what way do the mandibular processes contribute to facial development?

<p>The mandibular processes fuse medially to form the lower lip and chin, and laterally to the maxillary processes to form the cheeks.</p> Signup and view all the answers

What differentiates the maxillary processes' growth pattern from that of the mandibular processes?

<p>Maxillary processes grow medially to form the upper lip and laterally to form cheeks, while mandibular processes primarily form the lower lip and chin.</p> Signup and view all the answers

During the development of the respiratory system, which structure separates the esophagus and the laryngo-tracheal tube?

<p>The tracheo-esophageal septum separates the esophagus dorsally from the laryngo-tracheal tube ventrally.</p> Signup and view all the answers

From which embryonic layer does the epithelial lining of the respiratory system arise?

<p>The epithelial lining of the respiratory system arises from the endoderm, except for the nose, which is derived from ectoderm.</p> Signup and view all the answers

Which pharyngeal arches contribute to the cartilage of the larynx and its skeletal muscles?

<p>The cartilage of the larynx and its skeletal muscles are formed from the 4th and 6th pharyngeal arches.</p> Signup and view all the answers

How many subdivisions of the bronchi develop before birth?

<p>Seventeen subdivisions of the bronchi develop before birth.</p> Signup and view all the answers

What embryonic sources give rise to the visceral and parietal pleura?

<p>The visceral pleura is formed from splanchnic lateral plate mesoderm, while the parietal pleura arises from somatic lateral plate mesoderm.</p> Signup and view all the answers

What happens to the laryngo-tracheal tube during its development?

<p>The laryngo-tracheal tube grows caudally, giving rise to the larynx, trachea, and two lung buds.</p> Signup and view all the answers

What is polyhydramnios and how can it lead to preterm birth in neonates?

<p>Polyhydramnios is the excessive accumulation of amniotic fluid, which may indicate underlying fetal anomalies such as esophageal atresia, potentially leading to preterm birth.</p> Signup and view all the answers

Describe the problem neonates face when having a tracheoesophageal fistula during breastfeeding.

<p>Neonates with a tracheoesophageal fistula may choke after breastfeeding due to the abnormal connection between the trachea and esophagus, allowing milk to enter the airway.</p> Signup and view all the answers

What is respiratory distress syndrome in neonates, and what causes it?

<p>Respiratory distress syndrome, or hyaline membrane disease, occurs due to insufficient surfactant in premature infants, leading to alveoli collapse and fluid accumulation.</p> Signup and view all the answers

Outline the different origins of the diaphragm during its development.

<p>The diaphragm originates from the central tendon (septum transversum), costal margins (lateral body walls), and multiple ligaments and crura from mesodermal structures.</p> Signup and view all the answers

What distinguishes a congenital diaphragmatic hernia from a parasternal hernia?

<p>A congenital diaphragmatic hernia (Bochdalek) involves a defect in the posterior-lateral diaphragm allowing abdominal contents into the thoracic cavity, while a parasternal hernia occurs between the sternal and costal origins.</p> Signup and view all the answers

What is the anatomical significance of the phrenic nerve in diaphragm development?

<p>The phrenic nerve, originating from the 3rd to the 5th cervical myotomes, is crucial for diaphragm muscle function and arises during the diaphragm's development.</p> Signup and view all the answers

Explain how congenital hiatus hernia affects the thoracic cavity.

<p>A congenital hiatus hernia occurs when the esophageal orifice shortens, allowing the upper stomach to herniate into the thoracic cavity, potentially causing respiratory complications.</p> Signup and view all the answers

What is the role of pleuroperitoneal membranes in diaphragmatic anomalies?

<p>The pleuroperitoneal membranes contribute to the formation of the diaphragm and can be involved in defects leading to congenital diaphragmatic hernias.</p> Signup and view all the answers

What is a common characteristic of the canalicular stage of lung development?

<p>Respiratory bronchioles begin to form as terminal bronchioles divide.</p> Signup and view all the answers

During which stage of lung development does surfactant production begin?

<p>Surfactant production begins in the saccular stage, around the 20th week.</p> Signup and view all the answers

What condition results from incomplete canalization of the larynx?

<p>Laryngeal web results from incomplete canalization.</p> Signup and view all the answers

What characterizes tracheo-malacia, and why is it significant?

<p>Tracheo-malacia is characterized by soft immature cartilage in the trachea, causing stridor.</p> Signup and view all the answers

How does laryngeal atresia affect airways, and what is its developmental cause?

<p>Laryngeal atresia leads to a blocked airway due to failed recanalization.</p> Signup and view all the answers

Explain how the palate is formed and its significance in oral cavity development.

<p>The primary palate forms from the inter-maxillary segment, creating an anterior triangular area carrying the four incisors, essential for separating the oral and nasal cavities.</p> Signup and view all the answers

Describe the role of the oro-nasal membrane in nasal cavity development.

<p>The oro-nasal membrane initially separates the nasal pits from the oral cavity, rupturing to allow connection between the two cavities during nasal cavity development.</p> Signup and view all the answers

What embryological failure leads to oblique facial cleft, and what anatomical structure is exposed?

<p>Oblique facial cleft results from the failure of fusion between the maxillary and lateral nasal folds, exposing the nasolacrimal duct on the surface.</p> Signup and view all the answers

What is the consequence of excessive fusion of the maxillary and mandibular processes?

<p>Excessive fusion of the maxillary and mandibular processes results in microstomia, characterized by a small mouth opening.</p> Signup and view all the answers

Identify the embryonic origin of the nasal conchae and explain their function.

<p>The nasal conchae develop as elevations of the lateral nasal walls, serving to increase the surface area of the nasal cavity for effective humidification and filtration of air.</p> Signup and view all the answers

What is the embryonic source of the olfactory epithelium, and why is it important?

<p>The epithelium in the roof of the nasal cavity becomes specialized from the ectoderm to form olfactory epithelium, which is crucial for the sense of smell.</p> Signup and view all the answers

Discuss the impact of failed fusion between medial nasal folds during lip formation.

<p>Failure of fusion between the medial nasal folds can result in median cleft lip, affecting both the central upper and lower lips depending on the specific fusion points.</p> Signup and view all the answers

What is the main consequence of lung agenesis or hypoplasia in neonates?

<p>It leads to significant respiratory distress and insufficient gas exchange.</p> Signup and view all the answers

Explain how the maxillary sinus develops and its typical development timeline.

<p>The maxillary sinus develops during fetal life and reaches its maximum size during puberty, distinguishing it from other paranasal sinuses which develop after birth.</p> Signup and view all the answers

How does a congenital diaphragmatic hernia typically affect lung development in a neonate?

<p>It allows abdominal contents to herniate into the thoracic cavity, compressing the lungs and inhibiting their development.</p> Signup and view all the answers

Identify the embryonic structure that gives rise to the muscular elements of the diaphragm.

<p>The muscular elements of the diaphragm arise from the 3rd, 4th, and 5th cervical myotomes.</p> Signup and view all the answers

What mechanism leads to respiratory distress syndrome in premature infants?

<p>Insufficient surfactant production results in collapsed alveoli, causing respiratory distress syndrome.</p> Signup and view all the answers

What are the implications of a tracheoesophageal fistula on neonates during feeding?

<p>It causes choking and aspiration during feeding due to the abnormal connection between the trachea and esophagus.</p> Signup and view all the answers

Describe the origin of the costal part of the diaphragm.

<p>The costal part of the diaphragm arises from the mesoderm of the lateral body walls.</p> Signup and view all the answers

What role do pleuroperitoneal membranes play in the formation of congenital diaphragmatic hernia?

<p>They are involved in the closure of the diaphragm and can lead to a hernia if there is a defect.</p> Signup and view all the answers

What distinguishes a retrosternal hernia from other types of congenital hernias?

<p>A retrosternal hernia occurs through a defect between the sternal and costal origins of the diaphragm.</p> Signup and view all the answers

How does the development of the secondary palate contribute to the formation of complete cleft palate?

<p>Complete cleft palate occurs due to the failure of the palatine shelves to fuse with each other, the nasal septum, and the premaxilla.</p> Signup and view all the answers

What embryological layers contribute to the muscle and connective tissue found in the respiratory system?

<p>The muscle and connective tissue of the respiratory system primarily arise from mesoderm.</p> Signup and view all the answers

What anatomical structures arise from the lung buds during the development of the respiratory system?

<p>The lung buds give rise to the larynx, trachea, and two primary lung buds.</p> Signup and view all the answers

Describe the formation of the pleural cavities and the mesodermal origins of their linings.

<p>Pleural cavities form when lung buds expand into the pericardio-peritoneal canals, with visceral pleura from splanchnic mesoderm and parietal pleura from somatic mesoderm.</p> Signup and view all the answers

What role do the 4th and 6th pharyngeal arches play in the development of the larynx?

<p>The cartilage of the larynx and its skeletal muscles are formed from the 4th and 6th pharyngeal arches.</p> Signup and view all the answers

What is the significance of the recanalization process in the laryngo-tracheal development?

<p>Recanalization is significant because it restores the airway after the initial obliteration caused by epithelial proliferation.</p> Signup and view all the answers

How do the right and left main bronchi differ in terms of their subdivisions?

<p>The right main bronchus forms 3 secondary bronchi and 10 tertiary bronchi, while the left forms 2 secondary bronchi and 8-10 tertiary bronchi.</p> Signup and view all the answers

Explain the developmental relationship between the tracheo-esophageal septum and the respiratory system.

<p>The tracheo-esophageal septum separates the esophagus dorsally and the laryngo-tracheal tube ventrally during early foregut development.</p> Signup and view all the answers

What are the two processes that form the primary palate and what do they give rise to?

<p>The two processes are the medial nasal folds, which fuse to form the pre-maxilla, and they give rise to the nasal septum, philtrum of the upper lip, central part of the upper jaw, primary palate, and the tip of the nose.</p> Signup and view all the answers

Explain the significance of the stomodaeum in embryonic development.

<p>The stomodaeum, or oral pit, is significant as it is the precursor to the mouth and plays a critical role in the formation of the buccopharyngeal membrane, which ruptures in the 5th week.</p> Signup and view all the answers

What embryonic structures contribute to the formation of the upper lip?

<p>The upper lip is formed by the fusion of the medial nasal folds with the maxillary processes.</p> Signup and view all the answers

Describe the developmental changes that occur in the fronto-nasal process during the 4th to 5th weeks.

<p>During this period, nasal placodes appear on the fronto-nasal process, which invaginate to form nasal pits, leading to the formation of medial and lateral nasal folds.</p> Signup and view all the answers

What effects do the mandibular processes have on facial structure development?

<p>The mandibular processes fuse medially to form the lower lip and chin and laterally with the maxillary processes to help form the cheeks.</p> Signup and view all the answers

How do the maxillary processes relate to the formation of the cheeks?

<p>Maxillary processes grow laterally to fuse with the mandibular processes, forming the cheeks.</p> Signup and view all the answers

What role do the lateral nasal folds play in nose development?

<p>The lateral nasal folds develop into the ala of the nose, providing the structure for the external nostrils.</p> Signup and view all the answers

Explain the arrangement of the pharyngeal arches and their relevance in development.

<p>The pharyngeal arches are six mesodermal thickenings arranged cranio-caudally, crucial for the development of various structures in the head and neck.</p> Signup and view all the answers

Flashcards

Pharyngeal Arches

Six mesodermal thickenings on each side of the pharynx, arranged from head to tail.

1st Pharyngeal Arch

The most prominent pharyngeal arch, formed by the maxillary and mandibular processes.

Stomodeum

The opening of the mouth, formed by the buccopharyngeal membrane.

Facial Muscle Development

Face muscles are derived from the mesoderm of the second pharyngeal arch and are innervated by the facial nerve.

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Fronto-nasal Process

A median prominence from the head fold, contributing to the development of the nose and upper lip.

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Upper Lip Development

The upper lip forms primarily from the maxillary process, except for the philtrum, which develops from the inter-maxillary segment.

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Nasal Placodes

Ectodermal thickenings on each side of the fronto-nasal process, which invaginate to form nasal pits.

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Lower Lip Development

The lower lip is formed from the fusion of the mandibular processes.

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Pre-maxilla/Inter-maxillary Segment

The fusion of the two medial nasal folds, formed by neural crest cells, which forms the nasal septum, philtrum of the upper lip, central part of the upper jaw, primary palate and nose tip.

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Nose - Ala Development

The ala (wings) of the nose develop from the lateral nasal folds.

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Maxillary Processes

The lateral parts of the 1st pharyngeal arch, which fuse with the medial nasal folds to form the upper lip and cheeks.

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Nasal Cavity Development - Initial Stage

The nasal pits deepen to form the primitive nasal sacs. These sacs are separated from the oral cavity by the oro-nasal membrane, which eventually ruptures.

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Mandibular Processes

The medial parts of the 1st pharyngeal arch, which fuse medially to form the lower lip and chin.

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Nasal Cavity Development - Separation

The formation of the secondary palate separates the nasal and oral cavities again.

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Nasal Conchae Development

The nasal conchae are formed as elevations on the lateral nasal walls.

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Nasal Septum Development

The nasal septum develops from the inter-maxillary segment.

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Secondary Palate Development

The process by which two shelf-like structures, arising from the inner side of the maxillary processes, fuse in the midline with the descending nasal septum to form the roof of the mouth.

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Cleft Palate

A birth defect that occurs when the roof of the mouth doesn't close completely during fetal development. This can involve the anterior palate (front part), posterior palate (back part), or both.

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Tracheo-esophageal Septum Development

The separation of the foregut into the esophagus and the laryngo­tracheal tube. This is a crucial step in forming the respiratory system.

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Endoderm in Respiratory System

The tissue that forms the lining of the respiratory system, except for the nose, which is derived from ectoderm.

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Recanalization of Respiratory Tract

The process where the epithelial lining of the respiratory tract proliferates, temporarily blocking the airway, before reopening during further development. This is essential for proper formation of the respiratory structures.

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Cartilage of Larynx Formation

The cartilage of the larynx and its skeletal muscles develop from the 4th and 6th pharyngeal arches.

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Cartilage of Trachea Formation

The cartilage of the trachea and its smooth muscles originate from the splanchnic mesoderm.

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Development of Pleurae

The lung buds expand into the pericardio-peritoneal canals during development, giving rise to the two layers of the pleura that enclose the lungs.

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Pseudo-glandular Stage

The stage of lung development from 1 to 4 months where only terminal bronchioles are formed, giving the lung a gland-like appearance.

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Canalicular Stage

The stage of lung development from 4 to 6 months where terminal bronchioles divide into respiratory bronchioles, which further divide into alveolar ducts, creating a network for air exchange.

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Saccular Stage

The stage of lung development from 6 to 9 months where primitive alveoli, the tiny air sacs, form and capillaries establish close contact, allowing for gas exchange. Type II pneumocytes start producing surfactant, a crucial substance for lung function.

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Alveolar Stage

The final stage of lung development, continuing until 8 years old, where mature alveoli with good contact with capillary endothelial cells are formed, resulting in efficient gas exchange.

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Tracheal Atresia

A condition where the trachea is abnormally narrow or blocked, often causing breathing difficulties.

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Polyhydramnios due to Esophageal Atresia

A condition where a neonate is born prematurely due to excessive amniotic fluid caused by a blockage in the esophagus.

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Choking after Breastfeeding due to Trachea-esophageal Fistula

A situation where a neonate experiences choking after breastfeeding because of an abnormal connection between the trachea and esophagus.

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Lung Agenesis or Hypoplasia

The complete absence or underdevelopment of lung tissue.

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Congenital Cysts of Lung

Abnormal pockets of air within the lung tissue.

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Accessory Lung Lobe

An extra piece of lung tissue that develops from the trachea or esophagus.

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Respiratory Distress Syndrome (Hyaline Membrane Disease)

A respiratory condition in premature infants caused by insufficient surfactant.

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Parasternal (Retrosternal/ Morgagni) Hernia

A condition where the abdominal contents herniate through a defect in the diaphragm between the sternum and ribs.

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Congenital Diaphragmatic Hernia (postero-lateral defect/ Bochdalek)

A condition where the abdominal contents herniate through a defect in the diaphragm at the back, often on the left side.

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Congenital Hiatus Hernia

A condition where part of the stomach protrudes into the chest cavity, often due to a weakness or opening in the diaphragm.

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What is the Stomodeum?

The oral pit or the opening of the mouth, formed during the development of the head by the rupture of the buccopharyngeal membrane.

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How is the upper lip formed?

The upper lip is largely formed by the maxillary process, except for the philtrum, which originates from the inter-maxillary segment.

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What does the fusion of the medial nasal folds create?

The medial nasal folds fuse to form the pre-maxilla or inter-maxillary segment, which gives rise to the nasal septum, philtrum of the upper lip, central part of the upper jaw, primary palate and nose tip.

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What forms the ala of the nose?

The ala or wings of the nose develop from the lateral nasal folds, contributing to the characteristic shape of the external nose.

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What is the secondary palate formed by?

The two shelves arising from the maxillary processes fuse in the midline with the descending nasal septum, forming the roof of the mouth.

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What is recanalization of the respiratory tract?

The process of the epithelial lining of the respiratory tract proliferating, temporarily blocking the airway, before reopening during further development. This is crucial for the formation of the respiratory structures.

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How are the pleurae formed?

The lung buds expand into the pericardio-peritoneal canals during development, giving rise to the two layers of the pleura that enclose the lungs.

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What happens in the canalicular stage of lung development?

The canalicular stage of lung development (4-6 months) is when terminal bronchioles divide into respiratory bronchioles, which further divide into alveolar ducts, creating a network for the exchange of air.

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What forms the philtrum of the upper lip?

The philtrum of the upper lip is formed by the inter-maxillary segment, which is the fused portion of the two medial nasal folds.

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Where do the alae of the nose develop from?

The alae of the nose, the wing-like structures on either side of the nostrils, develop from the lateral nasal folds.

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From what structure does the nasal septum develop?

The nasal septum, the partition between the two nasal cavities, develops from the inter-maxillary segment, which is formed by the fusion of the two medial nasal folds.

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What is oblique facial cleft?

Oblique facial cleft is a birth defect caused by the incomplete fusion of the maxillary process and lateral nasal fold. The exposed nasolacrimal duct is a characteristic manifestation.

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What causes a median cleft lip?

A median cleft lip is a congenital defect resulting from the incomplete fusion of either the medial nasal folds (forming the upper lip) or the mandibular processes (forming the lower lip).

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What is a unilateral or bilateral cleft lip?

Unilateral or bilateral cleft lip occurs when the medial nasal fold and the maxillary process fail to fuse properly. This can affect one or both sides of the lip.

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What is macrostomia?

Macrostomia is a birth defect characterized by an abnormally large mouth opening, caused by incomplete fusion of the maxillary and mandibular processes.

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What is microstomia?

Microstomia is a condition where the mouth opening is abnormally small due to excessive fusion of the maxillary and mandibular processes during development.

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Tracheo-esophageal Fistula

A condition where the esophagus and trachea don't separate properly during development, leading to an abnormal connection between the two.

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Laryngeal Atresia

A condition where the larynx, responsible for sound production, is underdeveloped, leading to a high-pitched wheezing sound called stridor.

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Laryngo-malacia

A condition where the cartilage of the larynx is weak and floppy, causing a characteristic wheezing sound during breathing, especially in babies.

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Tracheo-malacia

A condition where the cartilage of the trachea is weak, leading to a collapse of the trachea during inhalation, resulting in wheezing.

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What is the origin of the secondary palate?

The secondary palate develops from two shelf-like structures that arise from the inner side of the maxillary processes. These structures fuse in the midline with the descending nasal septum, forming the roof of the mouth.

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What is the soft palate and where is it located?

The soft palate is the non-ossified part of the palate located posterior to the nasal septum. It's flexible and helps with speaking and swallowing.

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What is a cleft palate?

A cleft palate occurs when the roof of the mouth doesn't close completely during fetal development. This can involve the front part (anterior palate), back part (posterior palate), or both.

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What is a complete cleft palate?

A complete cleft palate involves the failure of the palatine shelves to fuse with each other, the nasal septum, and the premaxilla, affecting the entire palate.

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How is the foregut separated into the esophagus and laryngo-tracheal tube?

The tracheo-esophageal septum develops in the upper part of the foregut, dividing it into the esophagus (dorsally) and the laryngo-tracheal tube (ventrally).

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What is the origin of the epithelial lining of the respiratory system?

The epithelial lining of the respiratory system is derived from endoderm, except for the nose, which is derived from ectoderm.

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What structures give rise to the cartilage of the larynx and its muscles?

The cartilage of the larynx and its skeletal muscles are formed from the 4th and 6th pharyngeal arches.

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What is the origin of the cartilage and muscles of the trachea?

The cartilage of the trachea and its smooth muscles develop from splanchnic mesoderm, a specialized type of tissue in the embryo.

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Esophageal Atresia and Polyhydramnios

Neonates may be born preterm due to poly-hydramnios caused by esophageal atresia.

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Study Notes

Embryology: Respiratory System Development

  • The pharynx has 6 mesodermal thickenings arranged cranio-caudally.
  • The first arch is the most prominent, formed by maxillary and mandibular processes.
  • The stomodeum (oral pit) forms between the forebrain and heart.
  • The buccopharyngeal membrane ruptures in the 5th week.
  • The respiratory system develops from the laryngotracheal tube, a ventral outgrowth of the foregut.
  • Initially, the epithelial lining of the respiratory system is endodermal in origin, except for the nose, which is ectodermal.

Face/Nose Development (4th-8th week)

  • The fronto-nasal process forms a median prominence from the head fold.
  • Two maxillary processes develop from the dorsal part of the first pharyngeal arch.
  • Two mandibular processes develop from the ventral part of the first pharyngeal arch.
  • Nasal placodes (ectodermal thickenings) on the fronto-nasal process appear in the 4th week.
  • These placodes invaginate to form nasal pits, and medial and lateral nasal folds appear in the 5th week.
  • Lateral nasal folds form the alae (wings) of the nose.
  • Medial nasal folds fuse, forming the premaxilla/intermaxillary segment, contributing to the nasal septum, philtrum, central upper jaw, and the primary palate.

Maxillary Process Changes

  • Maxillary processes grow medially to fuse with medial nasal folds, forming the upper lip.
  • They grow laterally to fuse with mandibular processes, forming the cheeks.
  • They grow superiorly, separating from lateral nasal folds via the nasolacrimal groove.
  • The groove develops into the nasolacrimal duct.
  • Mandibular processes fuse with each other medially to form the lower lip and chin.
  • Maxillary processes fuse with mandibular processes to form the cheeks.

Face Musculature

  • Face musculature originates from the mesoderm of the 2nd pharyngeal arch, with innervation from the facial nerve.
  • The upper lip is primarily formed from the maxillary process, except for the philtrum (formed by the intermaxillary segment).
  • The lower lip forms from the mandibular processes.

Palate Development

  • The primary palate is the anterior triangular area, carrying the incisors, and arises from the intermaxillary segment.
  • The secondary palate develops as shelf-like projections from the inner side of maxillary processes.
  • These shelves fuse in the midline with the descending nasal septum.
  • The soft palate forms from the non-ossified portion posterior to the nasal septum.

Anomalies of the Face

  • Oblique facial cleft: Failure of maxillary and lateral nasal folds fusion.
  • Cleft lip (harelip): Failure of medial nasal folds (central upper cleft lip) or mandibular processes (central lower cleft lip) fusion, unilateral or bilateral.
  • Macrostomia: An abnormally large mouth opening, due to incomplete fusion of maxillary and mandibular processes.
  • Microstomia: An abnormally small mouth opening, due to excessive fusion of maxillary and mandibular processes.

Larynx, Trachea, Bronchi, and Lung Development

  • The trachea and esophagus form from the laryngotracheal tube, a ventral outgrowth of the foregut.
  • The epithelial lining of the respiratory tract originates from endoderm.
  • Mesoderm forms cartilage and muscles of the larynx and trachea.
  • Lung buds form initially, then divide into left and right main bronchi, further branching into secondary and tertiary bronchi.
  • The epithelium undergoes recanalization.
  • Development progresses through pseudo-glandular, canalicular, saccular, and alveolar stages.

Development of Pleurae

  • The visceral pleura arises from the splanchnic lateral plate mesoderm.
  • The parietal pleura arises from somatic lateral plate mesoderm.
  • The pleural cavity is the space between the parietal and visceral pleura.
  • The lung development stages include pseudoglandular (1-4 months), canalicular (4-6 months), saccular (6-9 months), and alveolar (up to 8 years).

Anomalies of Larynx

  • Laryngeal atresia: Failure of recanalization.
  • Laryngeal web: Incomplete canalization.
  • Laryngomalacia: Soft immature laryngeal cartilage causing stridor (common cause of infant stridor).

Anomalies of Trachea

  • Tracheal atresia: Complete closure of the trachea.
  • Tracheomalacia: Soft tracheal cartilage causing stridor.
  • Tracheo-esophageal fistula: Abnormal partitioning of the cranial part of the foregut by the tracheo-esophageal septum, potentially causing esophageal atresia or tracheoesophageal fistula, impacting swallowing and breathing.

Lung Anomalies

  • Lung agenesis or hypoplasia: Absence or underdevelopment of the lungs.
  • Congenital cystic lesions: Cysts in the lungs of possible tracheal or esophageal origin.
  • Accessory lung lobes: Extra lobes in the lungs.
  • Respiratory distress syndrome (Hyaline membrane disease): Premature infants exhibit insufficient surfactant production.

Development of Diaphragm

  • Diaphragm development originates from the mesoderm.
  • Central tendon and sternal components arise from the septum transversum.
  • Costal elements derive from the lateral body walls.
  • Median and arcuate ligaments connect with adjacent abdominal structures.
  • Muscle arises from the mesentery of the esophagus.
  • Cervical myotomes provide innervation for the diaphragm.

Congenital Anomalies of Diaphragm

  • Parasternal (Morgagni) hernia: Visceral organs herniate through a defect between the sternum and ribs.
  • Bochdalek hernia: Visceral organs herniate through a posterior defect, commonly on the left side, into the pleural cavity, potentially compressing the lungs.
  • Congenital hiatus hernia: The esophagus or stomach herniates through a defect in the diaphragm (hiatus), potentially causing gastroesophageal reflux.

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